The present invention relates to a fixing apparatus for electrophotography, and more particularly to a thermal fixing apparatus combining the noncontact fusion method using an infrared radiation source with the contact fusion method using a heated roller.
In electrophotography, a toner image is usually thermally fixed to the paper to become permanent, and the conventional electrophotographic copier achieves this object by using a radiation heat source, a heated roller, a heated plate or an oven. In the first method, an infrared lamp is used as the radiation heat source and the necessary heat can be applied throughout the fixing step, but if the image density is low, the toner does not absorb the necessary heat to provide a satisfactorily fixed image. This defect can be eliminated by using a powerful heat source, but then, the fire hazard of and the size of the fixing apparatus are increased. In the second and third methods, the toner image is placed in direct contact with a heated roller or plate, and the heating efficiency is high enough to achieve comparatively good fixing even if the image density is low. But either method requires 4 to 5 minutes to warm the roller or plate to the desired temperature, and moreover, the roller or plate must be heated throughout the operation of the copier to maintain the fixing temperature nearly constant, resulting in high power consumption. The use of an oven also requires a fairly long warm-up period and sustained heating that leads to high power consumption.